Conventionally, in relation to a shielding device applied to an electric component that widely requires insulation and shielding, it is known to provide a sufficient distance between a terminal unit and metal in order to prevent an electric discharge. That is, it is known that a creepage distance is necessary to increase a dielectric strength (see, for example, Patent Literature 1).
Also conventionally, in a portable receiver that accommodates a circuit assembly connected to a built-in antenna in a housing, for the purpose of improving electrostatic withstand voltage properties, it is proposed that an insulating cover that covers a part of the built-in antenna is arranged in the housing, and a creepage distance from a space in the housing to the built-in antenna is set to be longer in order to increase an electrostatic withstand voltage for improving electrostatic withstand voltage properties (see, for example, Patent Literature 2).
Meanwhile, there is a housing for an electronic device unit that encloses a substrate having an electronic component mounted thereon, where the housing includes two cases constituted by dividing a box body, respective opening parts of these two cases are butted and joined to form the box body, and the substrate is accommodated in the housing. Conventionally, in this housing, a space is generated in a portion where the two cases are butted, and accordingly there is a problem that an electrostatic discharge affects the electronic component from outside. As a countermeasure to this problem, a method of providing an insulating sheet inside of a housing so as to cover the butted portion and a method of not providing an electronic component on a substrate immediately below the butted portion are proposed.